A new perspective – using bioenergy crops to alleviate global warming: Reflections from an LTER fellow

Jinho Lee is a PhD student in the Plant, Soil and Microbial Sciences Department at Michigan State University. He works in the Kravchenko lab with interests in carbon dynamics of soil.

Jinho in the lab
Jinho in the lab.

Today we are facing one of the biggest environmental challenges that our species has never faced, and one that is caused by our own actions. Since the Industrial Revolution, the worldwide carbon dioxide (CO2) emissions have increased due to use of C-based fossil fuels. This has resulted in global warming. 

To alleviate global warming and reduce the dependence on fossil fuels, several alternative energy sources have been recommended, such as wave and wind energy, geothermal power, bioenergy, and more. 

Bioenergy fuels, made from crops, has gained special attention. Cultivating bioenergy crops can help build soil carbon (C), which enhances soil fertility and quality, while having the added benefit of reducing atmospheric CO2 by C sequestration as a countermeasure to mitigate global warming. While other alternative energies aim to reduce current greenhouse gas emissions, I am confident that bioenergy is the only way, which has the potential to reduce CO2 that we have emitted. 

I chose to study biofuels because I am confident they can play a major role in reducing the CO2 that we have emitted. As part of the KBS LTER research team, I am looking at the root systems of biofuel crops and the pores they create in the soil. Within these pores, my research focuses on C dynamics to find new and best way of promoting more C sequestration in bioenergy cropping systems, looking into C-based interactions between plant diversity, physical micro-environment. 

I utilized two cropping treatments at the LTER Marginal Land Experiment (MLE) sites – switchgrass and mixed prairie. Switchgrass is a particularly promising bioenergy crop with high biomass production as a monoculture system. Prairie vegetation has high plant diversity, but lower biomass production compared to Switchgrass. I found that after 7 years of growth, the areas with high plant diversity (restored prairie) had a higher soil C content compared to the C in the monoculture system (switchgrass). 

Moreover, my research team reported a result that the relative abundance of pores in 30-180 µm size was higher in prairies in comparison to that in Switchgrass, potentially driving this pattern in soil C. However,  the dominance of larger pores can also allow water and oxygen supplies to resident microbial communities, stimulating their activities, and it results in higher mineralization of soil organic carbon (SOC) and newly added C into CO2. These results reveal that without process-based knowledge of specified C mechanisms on these two systems, it is not easy to determine why one accumulates more SOC into the system compared to the other.

Soil cores
Soil cores from Jinho’s ongoing research looking at the structure of soil pores in switchgrass and prairie treatments.

To gain more insight into what might be going on, my next step is to look closely at undisturbed soil cores. I collected three intact soil from four replicated plots of switchgrass and mixed prairie. I used five different Marginal Land Experiment sites (Lux Arbor, Escanaba, Rhinelender, Hancock, and Lake City). The entire cores were subjected to X-ray µCT scanning at Dr. Chitwood’s lab, Dept. Horticulture, MSU at 20-30 µm resolution, and they are on pre-processing stage. Data of soil pore characteristics will be obtained by analyzing more than 2000 slices of images from each core, and totally 114 cores straddled various soil conditions will be use for the comparison between switchgrass and restored prairie systems. The distribution of soil pore sizes will help me figure out whether the physical structure of the soil is one of the factors driving the differences in C sequestration between the two cropping treatments.

This study would have been difficult to be carried out without helps of KBS LTER, the Kravchenko lab as well as Michigan State University communities. I appreciate this opportunity to get involved with KBS LTER and always look forward to collaboration with you.